Method of grinding a workpiece having a cylindrical bearing surface and method for determining processing parameters

The present disclosure relates in general to a method of grinding a workpiece by means of a grinding wheel, the workpiece comprising a cylindrical bearing surface, a radially extending sidewall extending outward from the cylindrical bearing surface, and a curved transition portion connecting the cylindrical bearing surface with the sidewall. The present disclosure also relates to a method for determining processing parameters of such a grinding method

Application of the dimensionless Aggressiveness number in abrasive processes

The chip thickness is often used to characterize abrasive processes, particularly grinding. Unfortunately, because of the seemingly random nature of the geometrically undefined cutting points and difficulty in estimating the cutting-point density, chip thickness is notoriously difficult to quantify. Recently, the dimensionless Aggressiveness number has gained popularity because it circumvents the need to quantify the wheel topography and is applicable to any geometry in abrasive contact. This paper shows how the concept of dimensionless Aggressiveness number applies to the most common abrasive geometries and how it can be used to achieve practical results in a variety of applications

On geometry and kinematics of abrasive processes: The theory of aggressiveness

Due to the stochastic nature of the abrasive-tool topography, abrasive processes are difficult to model and quantify. In contrast, their macro geometry and kinematics are usually well defined and straightforwardly controlled on machine tools. To reconcile this seeming contradiction, a novel unifying modelling framework is defined through the theory of aggressiveness. It encompasses the arbitrary geometry and kinematics of a workpiece moving relative to an abrasive surface. The key parameter is the point-aggressiveness, which is a dimensionless scalar quantity based on the vector field of relative velocity and the vector field of abrasive-surface normals. This fundamental process parameter relates directly to typical process outputs such as specific energy, abrasive-tool wear and surface roughness. The theory of aggressiveness is experimentally validated by its application to a diverse array of abrasive processes, including grinding, diamond truing and dressing, where the aggressiveness number is correlated with the aforementioned measured process outputs

On mechanics and monitoring of plunge-roll rotary dressing of grinding wheels

A study is made into the mechanics and monitoring of rotary plunge-roll dressing of grinding wheels using a roll with multi-layer diamonds contained in a hybrid, metal-ceramic bond. A fundamental relationship is obtained between grinding/dressing specific energy and the dressing aggressiveness number Aggrd, revealing a distinct size effect. Results also indicate (i) a nearly linear relationship between grinding and dressing specific energy, and (ii) direct proportionality between dressing specific energy and the acoustic emission (AE) signal. SEM observations indicate that smaller Aggrd produces a grit-dulling phenomenon different from grinding-induced dulling of the grits by attrition, which causes rapid workpiece-material adhesion

Optimierung von Schleif- und Abrichtprozessen mit Hilfe der Theorie der Aggressivit\ue4t: Fallstudien aus der Praxis

In den ersten sechzig Jahren der Schleifforschung (1914-1974) wurden verschiedene dimensionslose Parameter eingef\ufchrt, um die grundlegende Mechanik eines Schleifkontakts zu beschreiben. Sp\ue4ter wurden diese Parameter durch verschiedene Spandickenmodelle ersetzt, die eine schwierige und oft uneindeutige Quantifizierung der Schleifscheibentopographie erforderten. Der Ansatz der Grundprinzipien ist vor kurzem durch die gro fe vereinheitlichende Theorie der Aggressivit\ue4t und die praktische Aggressivit\ue4tszahl wieder aufgetaucht. Diese ist ein dimensionsloser Parameter, der sich bei der Optimierung jedes beliebigen Schleifprozesses, einschlie flich Schleifen und Abrichten, als leistungsf\ue4hig erwiesen hat. Die Aggressivit\ue4tszahl erfreut sich inzwischen einer gr\uf6 feren Beliebtheit und wird verwendet, da sie die grundlegende Prozessgeometrie und -kinematik erfasst und gleichzeitig eine Quantifizierung der Schleifscheibentopographie \ufcberfl\ufcssig macht. In diesem Beitrag wird die Verwendung der dimensionslosen Aggressivit\ue4tszahl in mehreren Fallstudien aus der realen Produktion untersucht. Dabei wird gezeigt, wie das Konzept zur Optimierung industrieller Prozesse eingesetzt werden kann, z. B. beim Schleifen von Nocken- und Kurbelwellen, S\ue4gespitzenschleifen, Nutenschleifen, Doppelseitenschleifen und Abrichten von Diamantscheiben

A Novel and More Efficient Way to Grind Punching Tools

ABSTRACT A simulation model of punch grinding has been developed which calculates the instantaneous material-removal rate, arc length of contact and temperature based on the kinematic relationships between wheel and workiece and determines the optimum machine parameters to reduce cycle time and achieve a constant-temperature no-burn situation. Two basic outputs of the simulation model include arc length of contact and specific material-removal rate. A thermal model is included in the simulation to calculate maximum grinding zone temperature rise. A novel method is developed to constrain this temperature rise in the simulation. The thermal model inputs a constant value of specific grinding energy and the energy partition, which represents the fraction of the grinding energy conducted as heat to the workpiece. The simulation-based optimization can lead to a drastic reduction of grinding cycle time. Moreover, the limitation of maximum grinding zone temperature rise below the transitional temperature can help to avoid generation of workpiece thermal damage, which includes thermal softening, residual tensile stress, and rehardening burn. The grindability of high speed steel (HSS) is also discussed in terms of power consumption, specific grinding energy and undeformed chip thickness

Aeroelastic model and analysis of an active camber morphing wing

Morphing aircraft structures usually introduce greater compliance into aerodynamic sections, and therefore will affect the aeroelasticity with the potential risk of increased flutter. A low-fidelity model of an active camber morphing wing and its aeroelastic model are developed in order to investigate the potential critical speed by exploiting its chord-wise dimension and flexibility. Such a model may be used for conceptual design, where low fidelity models are used to explore and optimise a wide range of configurations. The morphing camber concept is implemented using a continuous representation of a two-segment structure with a rigid segment and a deformable part. The aeroelastic model is developed based on both steady and unsteady aerodynamic models, so that different parameters can be easily modified to examine changes in the flutter solutions. Of particular interest are the ratio of the morphing segment length to the chord, and its relative stiffness, as such morphing camber is potential operated using the deformable part as a flap. By comparing the results of the quasi-steady and unsteady aerodynamic models, it is shown that the quasi-steady aerodynamic model gives a more conservative prediction of the flutter speed. In addition, responses in phase space are simulated to show the fundamental aeroelastic behaviour of the morphing camber wing. It is also shown that the active compliant segment can be used to stabilise the morphing aircraft by using feedback control. This paper provides a system-level insight through mathematical modelling, parameter analysis and feedback control into dynamics applications of morphing camber

Method of grinding a workpiece and method for determining processing parameters

The present disclosure relates to a grinding method for grinding of non-circular workpieces with an improved productivity and quality of the resulting workpiece. The method comprises a first and a second stage. The rotational speed profile of the workpiece in the first stage is controlled with the purpose of maintaining a pre-selected maximum surface temperature of the workpiece during said first stage, and grinding of the workpiece in said second stage is performed while controlling an aggressiveness number of said second stage so as to achieve an intended final surface quality. The present disclosure also relates to a method for determining the processing parameters of such a grinding method wherein the first and the second stage of the grinding method are iterated to thereby determine the processing parameters leading to a high productivity and desired quality of the workpiece after grinding